1. Field of Invention
This invention pertains generally to inertial rate sensors and, more particularly, to a rate sensor with built-in redundancy for use in an automobile stability control system.
2. Related Art
In automobile stability control systems and other applications where safety is critical, redundancy is sometimes employed for greater reliability. That is presently being done on a somewhat limited basis in automobile braking systems, using two complete, stand-alone devices, with the outputs of the two devices being compared for a suitable match by the braking system. This provides a system which is more tolerant of sensor faults than systems which have only one sensor.
Redundancy itself is not a new concept in applications where high reliability is required, and examples of prior art redundant systems are found in U.S. Pat. Nos. 3,551,776, 3,663,879, 3,813,990, 3,881,670 and 4,105,900. In these systems, the outputs of a plurality of separate identical sensors (typically three) are compared by a control system which is an integral part of the redundant system to verify that the primary sensor is functional.
The use of multiple stand-alone sensors to achieve redundancy has certain disadvantages. Each sensor requires a separate mounting location, a separate mounting procedure, and separate cabling which must be routed to the particular mounting location. In applications such as automobiles where cost is critical, the added cost of additional sensors, multiple mounting
It is in general an object of the invention to provide a new and improved rate sensor and method with built-in redundancy.
Another object of the invention is to provide a rate sensor and method of the above character which are particularly suitable for use in automobile stability control systems.
Another object of the invention is to provide a rate sensor and method of the above character which overcome the limitations and disadvantages of the redundant sensors heretofore provided.
These and other objects are achieved in accordance with the invention by providing a redundant rate sensor and method in which inertial rate is monitored with a plurality of vibratory sensing elements mounted in a single enclosure, signals from the sensing elements are processed to provide an independent rate output signal for each of the sensing elements, and the independent rate output signals are delivered to a connector which is accessible externally of the enclosure.